Time-resolved photoluminescence study of PPV derivatives with electron — and hole — transporting moieties.

The decay dynamics of photoexcited poly[(2-carbazol)-p-phenylene-vinylene](PCzPV) and poly[(2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3, 4-oxadiazole) -p-phenylenevinylene](PPPDPV) were investigated. The cw photoluminescence spectrum of PCzPV is composed of well-resolved two emission bands and a weak but apparent emission band at much lower energy. On the other hand, PPPDPV exhibits a broad and featureless emission band. The photoluminescence decay PPPDPV is almost independent of excitation energy and temperature. However, when the side chain substituent is changed to carbazole, the overall decay dynamics strongly depend on the excitation wavelength as well as temperature. The decay time constant at 580 nm of photoexcited PCzPV is shortened with a change in the excitation energy from 400 nm to 300 nm at 13 K. These results in the PCzPV and PPPDPV are interpreted in terms of the electronic properties of substituent and excimer process between substituent and main chain.